As the summer vacation season opens, the Great Lakes are at their highest levels in history. While drought-parched communities in the New York area and the South are worrying about too little water, the headaches around the Great Lakes are about too much water.

Up and down the lakes, beaches are shrinking, piers are disappearing and roads are flooding. Residents worry that waterfront homes are too close to the shore to escape damage, and some officials fear that Michigan`s $11 billion-a- year tourist business will suffer.

The Great Lakes, the world`s largest body of fresh water, were 8 inches to 2 1/2 feet above normal last week, according to the Army Corps of Engineers. It forecasts that the water levels will climb 2 to 4 inches in June, and other experts predict that the rise will continue through the summer.

``Unless there is some significant weather change, things will get a little worse before they get better,`` said James Fish, executive director of the Great Lakes Commission, a non-profit research organization that deals with water and economic issues. ``The damage will probably be the highest ever, too.``

Officials attribute the high water to precipitation that was 21 percent above normal from October through March. In the last half of that period, precipitation was 40 percent above normal. Heavy snow and spring rains caused flash floods in some communities and speeded the pace of erosion in others.

``We`ve got 4,000 feet of shoreline that`s out in the lake,`` said Dick Holmberg, an erosion prevention specialist in Whitehall, Mich., on Lake Michigan. ``We`re talking damage in the millions of dollars, but I say it`s priceless because you can`t really replace a beach.``

The problems are not limited to Lake Michigan. In Gibraltar, Mich., on the Detroit River, a major tributary of Lake Erie, Arthur J. Redmond, the town`s public works director, has helped lift 17,000 sandbags to keep out the water. The next time there is a flood, Redmond does not want his neighbors` living rooms to be the flood basin.

Officials say it is too soon to estimate the damage or the repairs that will be needed. But they are concerned that tight local budgets will not be able to cover the costs.

In Traverse City, Mich., where sections of four beaches and a $180,000 city-owned walkway are under water, budget-conscious officials worry that they cannot afford another year like 1985.

``What can you do -- go to Chicago and pull the plug?`` remarked Dale Majerczyk, Traverse City`s director of public services. ``When we built that walkway three years ago, we built it just above the highest watermark ever recorded.``

But hydrologists have been rewriting the record books this year. Lakes Michigan and Huron were 3 inches above record last week, while Lake Erie was 27 inches higher than it usually is at this time of year, according to the Corps of Engineers.

Lake Superior was 9 inches above its normal level. All the lakes except Ontario have reached record high levels at times this spring.

``We`ve been on the high side of average for months,`` said Ross Kittleman, a regional Army Corps of Engineers official. ``It`s been like filling a bathtub. You put the water in at one end and it goes up at the other end.``

There is nothing new about high water in the 795,000-square-mile Great Lakes basin, where water levels have been shown to run in cycles, rising for about seven years and falling for about five.

In 1952 high water caused damage estimated at $88 million in a summer in which 80 homes and cottages toppled into Lake Michigan. Most of the records broken this year were set in 1973.

But this time the surge caught many communities unprepared, even though Albert Ballert of the Great Lakes Commission says the warning signs had been visible for years.

Annual precipitation has been rising since 1977, he said, and lake levels have followed. Precipitation averaged about 4 inches above normal on Lakes Huron and Erie last year, Ballert said.

He said that at Watertown, N.Y., near Lake Ontario, the precipitation has been rising steadily in recent years and that the trend appeared to be continuing.

Erosion, another factor in this year`s headaches, has also increased in recent years, and there is debate on whether new lakefront homes have accelerated it. After the high-water years of the 1970s, Michigan adopted guidelines that require new structures to be set back from the waterfront 35 to 95 feet.